Eyal Feigenbaum

Unity-order index change in transparent conducting oxides at visible frequencies.

We report a method for obtaining unity-order refractive index changes in the accumulation layer of a metal-oxide-semiconductor heterostructure with conducting oxide as the active material. Under applied field, carrier concentrations at the dielectric/conducting oxide interface increase from 1 x 10(21)/cm(3) to 2.8 x 10(22)/cm(3), resulting in a local refractive index change of 1.39 at 800 nm. When this structure is modeled as a plasmonic waveguide, the change corresponds to a modal index change of 0.08 for the plasmonic mode.

Efficient Coupling between Dielectric-Loaded Plasmonic and Silicon Photonic Waveguides

The realization of practical on-chip plasmonic devices will require efficient coupling of light into and out of surface plasmon waveguides over short length scales. In this letter, we report on low insertion loss for polymer-on-gold dielectric-loaded plasmonic waveguides end-coupled to silicon-on-insulator waveguides with a coupling efficiency of 79 ± 2% per transition at telecommunication wavelengths. Propagation loss is determined independently of insertion loss by measuring the transmission through plasmonic waveguides of varying length, and we find a characteristic surface-plasmon propagation length of 51 ± 4 μm at a free-space wavelength of λ = 1550 nm. We also demonstrate efficient coupling to whispering-gallery modes in plasmonic ring resonators with an average bending-loss-limited quality factor of 180 ± 8.

Resonant guided wave networks.

A resonant guided wave network is an optical materials design consisting of power-splitting elements arranged at the nodes of a waveguide network. The resulting wave dispersion depends on the network layout due to localized resonances at several length scales in the network. These structures exhibit both localized resonances with a Q approximately 80 at 1550 nm wavelength as well as photonic bands and band gaps in large periodic networks at infrared wavelengths.

Ultrasmall Volume Plasmons, yet with Complete Retardation Effects

Nanoparticle plasmons are attributed to quasistatic oscillations with no wave propagation due to their subwavelength size. However, when located within a band-gap medium (even in air if the particle is small enough), the particle interfaces act as wave mirrors, incurring small negative retardation. The latter, when compensated by a respective (short) propagation within the particle, generates a constructive interference based resonator. The unusual wave interference in the subwavelength regime (modal volume <0.001lambda(3)) significantly enhances the Q factor, e.g., 50 vs 5.5 of the quasistatic limit.

Synthesis and Characterization of Plasmonic Resonant Guided Wave Networks

Composed of optical waveguides and power-splitting waveguide junctions in a network layout, resonant guided wave networks (RGWNs) split an incident wave into partial waves that resonantly interact within the network. Resonant guided wave networks have been proposed as nanoscale distributed optical networks (Feigenbaum and Atwater, Phys. Rev. Lett. 2010, 104, 147402) that can function as resonators and color routers (Feigenbaum et al. Opt. Express 2010, 18, 25584-25595). Here we experimentally characterize a plasmonic resonant guided wave network by demonstrating that a 90° waveguide junction of two v-groove channel plasmon polariton (CPP) waveguides operates as a compact power-splitting element. Combining these plasmonic power splitters with CPP waveguides in a network layout, we characterize a prototype plasmonic nanocircuit composed of four v-groove waveguides in an evenly spaced 2 × 2 configuration, which functions as a simple, compact optical logic device at telecommunication wavelengths, routing different wavelengths to separate transmission ports due to the resulting network resonances. The resonant guided wave network exhibits the full permutation of Boolean on/off values at two output ports and can be extended to an eight-port configuration, unlike other photonic crystal and plasmonic add/drop filters, in which only two on/off states are accessible.

Programming of inhomogeneous resonant guided wave networks

Photonic functions are programmed by designing the interference of local waves in inhomogeneous resonant guided wave networks composed of power-splitting elements arranged at the nodes of a nonuniform waveguide network. Using a compact, yet comprehensive, scattering matrix representation of the network, the desired photonic function is designed by fitting structural parameters according to an optimization procedure. This design scheme is demonstrated for plasmonic dichroic and trichroic routers in the infrared frequency range.

Dielectric based resonant guided wave networks

Resonant guided wave networks (RGWNs) are demonstrated to operate based on dielectric waveguides, broadening the scope of this optical design approach beyond plasmonics. The intersection of two dielectric waveguides that is modified by a tuned scattering particle is shown to function as an equal power splitting element, a key enabler of resonant guided wave networks. We describe structures composed of two types of waveguides, Si slabs and SOI ribs, at the telecom frequencies using both, Au and etch, based scatterers.

Negative Group Velocity: Is It a Negative Index Material or Fast Light?

When negative slop of the dispersion curve is encountered – the propagating light may be either ‘fast light’ or ‘backward propagating’. We show that the same photonic (plasmonic) system can support both these disjoint solutions.

Interference effects in laser-induced plasma emission from surface-bound metal micro-particles

The light-matter interaction of an optical beam and metal micro-particulates at the vicinity of an optical substrate surface is critical to the many fields of applied optics. Examples of impacted fields are laser-induced damage in high power laser systems, sub-wavelength laser machining of transmissive materials, and laser-target interaction in directed energy applications. We present a full-wave-based model that predicts the laser-induced plasma pressure exerted on a substrate surface as a result of light absorption in surface-bound micron-scale metal particles. The model predictions agree with experimental observation of laser-induced shallow pits, formed by plasma emission and etching from surface-bound metal micro-particulates. It provides an explanation for the prototypical side lobes observed along the pit profile, as well as for the dependence of the pit shape on the incident laser and particle parameters. Furthermore, the model highlights the significance of the interference of the incident light in the open cavity geometry formed between the micro-particle and the substrate in the resulting pit shape.

Silicon coupled channel plasmonic nano-circuits: 4-way power splitting and resonant networks

We demonstrate efficient coupling into channel plasmon polariton waveguides from Si ridge waveguides at λ0 = 1520nm, using near-field scanning-optical measurements. We further demonstrate optical power splitting at ultracompact 90-degree 4-way splitters and 2x2 resonators.